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History
The Battery Opens the Laboratory
Sustained current changes what electrical science can do
The voltaic pile did something that friction machines and Leyden jars could not: it provided a continuing source of electrical current.
Static machines could create high voltages, and Leyden jars could store charge and release it suddenly. The battery made it possible to keep current flowing long enough to watch chemical, thermal, magnetic, and physiological effects develop over time.
electricity could now be used as a steady laboratory tool instead of only as a spark, shock, or brief discharge.
From a pile of discs to a practical source
Volta's pile used repeated pairs of dissimilar metals separated by material moistened with an electrolyte. Each pair contributed a small electrical potential. Connecting many pairs in series increased the total voltage.
Early piles were troublesome: electrolyte leaked, metals corroded, and the output changed with use. But the principle was revolutionary.
Measurement trail 5 — electrical potential: the volt (V)
A battery establishes an electrical potential difference between its terminals. The unit is the volt, symbol V, named for Alessandro Volta.
Because we already introduced the joule of energy and the coulomb of charge, we can now give the volt a precise relationship:
One volt means that each coulomb of charge changes energy by one joule as it moves through that potential difference.
The practical volt was standardized during the nineteenth-century international effort to make electrical measurements agree from laboratory to laboratory. Standard chemical cells, including the Clark and later Weston cells, became reproducible references for comparing voltages.
Water begins to come apart
Soon after Volta announced his pile, William Nicholson and Anthony Carlisle passed current through water and observed gases forming at the electrodes. Electricity could therefore do more than make sparks or move muscles: it could cause chemical change.
Electrolysis
The use of electric current to drive chemical change became known as electrolysis. It became one of the great bridges between electricity and chemistry.
Humphry Davy — electricity becomes a chemical tool
The British chemist Humphry Davy built powerful battery arrangements and used electrical current to break apart compounds that resisted ordinary chemical methods. His work led to the isolation of several highly reactive elements, including potassium and sodium.
| Before sustained current | With the battery |
|---|---|
| Electrical effects were often brief. | Current could flow for seconds, minutes, or longer. |
| Static attraction and sparks dominated demonstrations. | Chemical changes could be watched continuously. |
| Stored charge had to be discharged and recharged. | The source kept driving the circuit while chemical action continued. |
| Many experiments were dramatic but transient. | Experiments became increasingly repeatable and measurable. |
Heat and light
Current flowing through conductors could produce heat. Powerful batteries also made sustained electrical arcs possible. Davy demonstrated brilliant arcs between carbon conductors. The electric arc would later become important in lighting, furnaces, welding, and other technology.
The circuit becomes easier to study
With a sustained source, the idea of a complete electrical circuit became increasingly concrete. An experimenter could open the path, close it, make it longer, pass it through a solution, or substitute one material for another while the effect continued.
- Does current pass through this material?
- What happens when the wire is made longer?
- What happens when more cells are added?
- What happens when the circuit is broken?
- What happens when current passes through a liquid?
The battery gives magnetism a new role
For centuries magnetism had meant lodestones, magnets, and compass needles. Electricity and magnetism still seemed like separate subjects. But a steady current allowed one decisive experiment: place a compass near a wire while current flows.
electric current creates a magnetic field.